應用介電泳效應在微流道中分離粒子之研究：以水滴形結構產生不均勻電場為基礎

Abstract

近年來，隨著生物分析需求的提升，微流體因具備體積小、樣品用量低、反應快速等優勢，漸漸成為分析化學與生醫領域中的重要工具。如何在微米尺度下操縱流體與懸浮物質的運動，是相關領域中重要的課題。介電泳(Dielectrophoresis, DEP)是一種藉由非均勻電場誘發粒子極化，進而操控其運動的現象，適用於帶電與不帶電的可極化粒子。由於其免標記和非接觸式操作的優點，介電泳被應用於物質的分離、濃縮及捕獲等用途。然而，介電泳效果取決於微流體裝置的構型設計以及電場配置，因此裝置的改良成為提升分離效果的挑戰之一。 本研究承接前人設計基礎，提出並且優化一種絕緣式介電泳分離裝置，核心結構採用水滴形設計，以產生不均勻電場並引發正介電泳力，促使粒子於通道中因介電泳而產生偏移，並在結構陣列中持續累積的偏移，以實現分離效果。本研究使用次微米尺寸的聚苯乙烯粒子作為目標分離對象，探討不同粒徑的粒子在各種電場條件下之偏移行為。由於在微米尺度下，即使是微小的結構幾何更動，也可能造成局部電場劇烈變化，進而導致粒子路徑的改變。本研究針對微流道設計進行多次調整，涵蓋流道截面尺寸、鞘流配置與結構陣列間距等參數，目的是在操作門檻與電場分布特性之間取得平衡，以兼顧分離效果與系統穩定性。 我們在研究中先透過COMSOL Multiphysics模擬分離裝置中的電場，以優化裝置幾何參數與電場設計。實驗部份則使用100nm、200nm、500nm和750nm之螢光聚苯乙烯粒子，在顯微鏡下觀測粒子在裝置中的移動情形和分離效果。 實驗結果顯示，粒子粒徑越大者所受之介電泳力越強，偏移效果也越明顯，由此成功實現不同粒徑粒子的分離。本研究驗證了水滴形結構對於粒子分離的效果，提供了一種可拓展至其他分子的分離技術，未來可應用於生醫分子、細胞或奈米粒子的高效率篩選與分析，展現其應用潛力。

In recent years, the growing demand for bioanalytical applications has highlighted the advantages of microfluidic systems, including reduced sample volume, compact device size, and rapid reaction times. As a result, microfluidics has become an essential tool in analytical chemistry and biomedical engineering. A key challenge in this field lies in effectively manipulating fluids and suspended particles at the microscale. Dielectrophoresis (DEP), a phenomenon in which polarizable particles are influenced by non-uniform electric fields, offers a label-free and non-contact method for particle manipulation. It is applicable to both charged and neutral particles and has been widely employed for separation, concentration, and trapping. However, the performance of DEP-based systems is highly dependent on device geometry and electric field configuration, making structural optimization critical for enhancing separation efficiency. In this study, we build upon previous designs to propose and optimize an insulator-based dielectrophoresis (iDEP) device that features droplet-shaped structures. These structures induce non-uniform electric fields which lead to positive DEP forces, causing lateral displacement of particles as they traverse the channel. By arranging these structures in an array, cumulative displacement is achieved, enabling effective particle separation. Submicron polystyrene particles with diameters of 100 nm, 200 nm, 500 nm, and 750 nm were used to evaluate the separation performance under various electric field conditions. Given the sensitivity of electric field distribution to microscale geometric changes, the microchannel design was iteratively refined. Key parameters—such as channel cross-section, sheath flow configuration, and spacing between structural elements—were adjusted to balance operational simplicity with electric field control, ensuring both separation performance and system stability. Electric field simulations were conducted using COMSOL Multiphysics to guide the optimization of device geometry and voltage configurations. Experimental validation was performed by tracking the motion of fluorescent polystyrene particles under a microscope. The results show that larger particles experienced stronger dielectrophoretic forces and more significant lateral displacement, confirming successful size-based separation. This work demonstrates the effectiveness of droplet-shaped structures in enhancing DEP-based separation and provides a scalable approach for sorting biomolecules, cells, or nanoparticles. The proposed design holds significant potential for future applications in biomedical analysis and high-throughput screening.